It is known that organopolysiloxanes containing Si-bonded vinyl groups can be reacted with organopolysiloxanes containing Si-bonded hydrogen atoms in the presence of catalysts. However, such organopolysiloxanes containing Si-bonded vinyl groups are not readily available since they have to be prepared by hydrolysis from halovinylsilanes, and they can only be prepared with difficulty.
Organopolysiloxanes containing trimethylolethanediallyl ether, trimethylolpropane-diallyl ether or pentaerythritol-triallyl ether groups, which are described in U.S. Pat. No. 4,311,821 (published Jan. 19, 1982, C. Weitemeyer et al, Th. Goldschmidt AG), are more readily available. The linking of the trimethylolethane diallyl ether, trimethylolpropane-diallyl ether or the pentaery-thritol-triallyl ether is achieved by reaction of the hydroxyl group with an Si-bonded halogen or Si-bonded alkoxy group of an organopolysiloxane. The disadvantage is that the SiOC linkage thus obtained is relatively unstable to hydrolysis in comparison with an SiC linkage.
The reaction of an organic compound containing four aliphatic double bonds, such as, for example, tetraallyloxyethane, with a silane containing Si-bonded hydrogen in the presence of a catalyst which promotes the addition of an Si-bonded hydrogen atom to an aliphatic double bond is described in U.S. Pat. No. 4,208,319 (published Jun. 18, 1980, P. August et al, Wacker-Chemie GmbH). In this reaction, yields of organosilane containing 3 aliphatic double bonds of practically 100 percent of theory are obtained. The organosilanes thus obtained are used as reinforcing additives in compositions which are based on organic polymers and fillers and can be crosslinked by sulfur or free radicals.
An object of the present invention is to provide siloxane copolymers which contain alkenyl groups Another object of the present invention is to provide a simple process for preparing siloxane copolymers containing more than one alkenyl group on a silicon atom. A further object of the present invention is to provide siloxane copolymers containing more than one alkenyl group on a silicon atom which are stable to hydrolysis. A still further object of the present invention is to provide siloxane copolymers having more than one alkenyl group which rapidly crosslink with organopolysiloxanes containing Si-bonded hydrogen atoms in the presence of a catalyst which promotes the addition of Si-bonded hydrogen to an aliphatic double bond.